He definitely understands everything he’s hearing when they talk. The cute scene where he pops his head in upside down while Mando and Cara Dune are talking? He was overheating them discussing the plan to go back to the client. He listened in and was like “hell naw” and then started trying to turn the ship around. First time I watched it I thought it was just another cute scene of him playing around with buttons on the ship, but no, he’s frantically trying to turn the ship around to avoid going back to dude who was likely torturing him with experiments.